1. Field of the Invention
This invention generally relates to a deployment system for deploying a tubular medical device. More particularly, this invention relates to an everting deployment system for tubular medical devices and a handle for receiving and splitting a tubular member, such as a catheter wall.
2. Background of the Invention
Various diseases of blood vessels may cause a stenosis or occlusion, partially or completely, of the lumen of the blood vessel, which can result in a decrease or complete loss of function. The wide spread occlusion of such diseases demands a number of new methods of medical treatment. Prosthetic devices or stents for sustaining a blood vessel lumen typically have a tubular shaped frame which is introduced in the vessel and fixed in the necessary place to sustain the lumen of the body vessel. One such prosthetic device includes a tubular shaped wire frame with a plurality of interconnected cells and flexible interconnections. The device is collapsible and is contained in a tubular sheath for introduction into the body of a patient. When the device is positioned in the occluded region of the body vessel, it is released from the tubular sheath and permitted to expand radially against the wall of the body vessel.
There are many types of introducers. One such type is the push/pull type of introducer. The push/pull type of introducers includes the category of introducers that require pushing the prosthetic device out of the distal end relative to the sheath or pulling the sheath in the proximal direction relative to the prosthetic device. Regardless, these introducers induce sliding interaction forces between the prosthetic device and the sheath.
The sliding interaction forces may be adverse for a number of reasons. One is the sliding interaction forces between the introducer and a drug coated prosthetic device and the sheath may affect the integrity of the coating or may even rub off the coating. Furthermore, the drug coating of the prosthetic device may present a “sticky” surface that result in a greater frictional force that must be overcome when using these introducers. Another reason is the sliding interaction forces between the introducer and a stent with a graft covering or an implantable valve with valve material. In both instances the integrity of the graft or valve material may be affected, including being torn or stressed. Furthermore, longer stents, especially self-expanding stents, present greater frictional forces to overcome when deploying. This is primarily due to the increased area of contact between longer stents and the luminal wall of the introducer. The longer self-expanding stents may also have greater radial expanding forces against the luminal wall of the introducer that also need to be overcome during deployment with these introducers.
Another type of introducer, described in more detail below, may be called a rolling membrane, roll sock, or everted liner introducer. This type of introducer is particularly beneficial to overcome the problems of the push/pull introducer. The everted liner introducer typically has a sheath connected to an inner member disposed within the sheath by an everted liner. The everted liner is folded on itself and can define a stent retaining region where the prosthetic device is loaded. During deployment, the sheath and the inner member move relative to one another to peel the everted liner away from the prosthetic device. At least one advantage of the everted liner introducer is the ability to deploy the prosthetic device without inducing the sliding interaction forces between the prosthetic device and the luminal wall of the introducer. Instead, during deployment the prosthetic device remains relatively stationary while the everted liner is rolled away from the prosthetic device thus substantially eliminating the sliding interaction forces.
One limitation of the everted liner introducer is the amount of length the sheath must be pulled in the proximal direction to deploy the prosthetic device. Because the everted liner is folded on itself, the sheath typically must be pulled back about twice as far as the length of the prosthetic device to deploy the prosthetic device. For example, for a 140 mm prosthetic device, the sheath must be pulled back about 280 mm. This can make the handle very long and cumbersome to operate. As a result, it also becomes difficult for the physician to regulate and maintain the portion of the sheath that is pulled back.
Another limitation can be stent jumping. Stent jumping is primarily the ability of the prosthetic device to jump or move during deployment due to the radial force exerted by a partly exposed prosthetic device acting to pull the unexposed portion from the stent retaining region. Stent jumping can cause the prosthetic device to deploy prematurely, deploy to an unintended location, and/or cause damage to the vessel wall due to the impact of the tubular medical device suddenly exiting the stent retaining region. Flushing air from the stent retaining region and catheter prior to deployment may also be problematic because the inner member is disposed within the lumen of the sheath, leaving very little area for the flushing fluid to travel. Since the everted liner must be rolled on the prosthetic device during loading while maintaining the prosthetic device in the compressed configuration, loading the prosthetic device within the everted liner of the everted liner system can also be problematic.